The present invention relates to a lubricating oil for a compression refrigerating machine, which is used together with a hydrofluorocarbon refrigerant and a refrigerating/air-conditioning machine using the same.
Many attempts have hitherto been made to prevent choking phenomena in capillary tubes and expansion valves caused by contaminants generated by changing refrigerant systems from hydrochlorofluorocarbon (HCFC) to hydrofluorocarbon (HFC). For example, in xe2x80x9cRefrigerator and Refrigerant Compressorxe2x80x9d disclosed in JP-A 103616/1995, a filter composed of a membrane material, such as fluororesin and cellulose mixed ester, is used in a refrigerant passage. In addition, in xe2x80x9cRefrigerator and Refrigerant Compressorxe2x80x9d disclosed in JP-A 235569/1994, a filter composed of a porous sintered metal and having a pore size of not more than 80 xcexcm is inserted in a dryer of a refrigerating machine. Further, in xe2x80x9cRefrigeratorxe2x80x9d disclosed in JP-A 105673/1996, the removal of sludge is performed by blowing capillary tubes with a high-pressure gas during the operation.
In addition, in xe2x80x9cRefrigerating Cyclexe2x80x9d disclosed in JP-A 247582/1996, in order to prevent various kinds of harm caused by the accumulation of contaminants generated during refrigerating cycling,
(1) a plurality of mechanisms provided with a tube charged with a filler or a branching valve for dividing a refrigerant passage are used as a throttling mechanism; and
(2) a scavenging tube is provided through a directional control valve apart from a regular passage, or
(3) a synthetic ester oil and a mineral oil of any one of a naphthene mineral oil, a paraffin mineral oil and an alkyl benzene mineral oil are used at a specified ratio as a lubricating oil for a compressor. Further, in xe2x80x9cRefrigerator Composition and Refrigerating Cyclexe2x80x9d disclosed in JP-A 143486/1997, a refrigerating machine oil containing a base oil composed of a mixture of 5-30 parts by weight of any one of mineral oils of a naphthene mineral oil, a paraffin mineral oil, a poly xcex1-olefin mineral oil and an alkylbenzene mineral oil, and 70-95 parts by weight of polyol ester is used in order to prevent the choking phenomenon caused by an ester refrigerating machine oil.
However, in the cases of xe2x80x9cRefrigerator and Refrigerant Compressorxe2x80x9d disclosed in JP-A 103616/1995, xe2x80x9cRefrigerator and Refrigerant Compressorxe2x80x9d disclosed in JP-A 235569/1994, xe2x80x9cRefrigeratorxe2x80x9d disclosed in JP-A 105673/1996, and xe2x80x9cRefrigerating Cyclexe2x80x9d disclosed in JP-A 247582/1996, there is a problem that a filter, a high-pressure gas blower, a throttling mechanism charged with a filler, and a tube for scavenging contaminants are additionally required since the previous refrigerators and air conditioners can not be used as they are, leading to an increased cost. In addition, when the aforementioned filters are utilized, there arises a further problem that the filters themselves are clogged.
In addition, in the cases of xe2x80x9cRefrigerating Cyclexe2x80x9d disclosed in JP-A 247582/1996 and xe2x80x9cRefrigerator Composition and Refrigerating Cyclexe2x80x9d disclosed in JP-A 143486/1997, the above refrigerating machine oil has bad miscibility with HFC refrigerants and, especially in the case of R410A, there is a problem that an amount thereof to be mixed is highly restricted. Further, there is also a problem that, depending upon the operating conditions, the occurrence of deflection in the ratio of the mixed oil within the refrigerating machine reduces the efficiency for washing capillary tubes.
The present invention was done to overcome the above previous drawbacks. It is an object of the present invention to provide a lubricating oil, which can prevent choking caused by contaminants in capillary tubes and expansion valves in the use of a HFC refrigerant, for a compression refrigerating machine without any modification of the machine, and a refrigerating/air-conditioning machine using the same.
In order to attain the above object, the present invention features a lubricating oil for a compression refrigerating machine, used together with a HFC refrigerant, which comprises a compound having the following general formula:
R1(R2O)n(R3O)mR4
wherein R1: any one of alkyl group, alkoxy group and aryl group;
R2: alkylene group having a carbon number of 2-4;
R3: alkylene group having a carbon number of 2-4;
R4: hydrogen or alkyl group.
In this essential feature, a compound having the miscibility with a HFC refrigerant and the solubility with contaminants generated in the use of the HFC refrigerant is added to the present lubricating oil for a compression refrigerating machine. Therefore, the deflection in the ratio between the present lubricating oil and the HFC refrigerant within the above refrigerating/air-conditioning machine is not caused by using the present lubricating oil together with a HFC refrigerant as a working fluid for a compression refrigerating machine. Therefore, the reduction in the efficiency for washing capillary tubes and expansion valves can be prevented. That is, according to the present invention, the reliability of the refrigerating/air-conditioning machine using the HFC refrigerant may be enhanced without any modification thereof.
In addition, the present invention features a polyvinyl ether lubricating oil for a compression refrigerating machine, used together with a HFC refrigerant, which comprises a compound added at an amount of not less than 5 wt % and not more than 10 wt %, said compound having the following general formula:
R1(C4H8O)n(R5O)mR4
wherein R1: any one of alkyl group, alkoxy group and aryl group;
R4: hydrogen or alkyl group;
R5: alkylene group having a carbon number of 2-3;
n/m: 1/9-10/0.
In this essential feature, since the above compound contains butylene oxide (C4H8O) having a carbon number of 4, the solubility with the HFC refrigerant and the contaminants is very good. Moreover, the compound is added to the present polyvinyl ether lubricating oil for a compression refrigerating machine at an amount of not less than 5 wt %. Therefore, the rate of flow reduction caused by choking in the capillary tubes, expansion valves and the like of a refrigerating/air-conditioning machine using the present lubricating oil and the HFC refrigerant as a working fluid, can be sufficiently decreased to 0%-10%, and the choking caused by contaminants in capillary tubes and expansion valves can be effectively prevented. Further, since the amount of the above compound to be added to the present lubricating oil is not more than 10 wt %, the reduction in volume insulation resistance for the present lubricating oil as a whole can be decreased. Therefore, it is not possible that leakage current from a hermetic motor increases. That is, according to the present invention, the reliability of the refrigerating/air-conditioning machine using a HFC refrigerant may be enhanced without any modification thereof.
In addition, the present invention features a refrigerating/air-conditioning machine equipped with a compressor using a HFC refrigerant and a lubricating oil as a working fluid, which comprises a compound having the following general formula:
R1(R2O)n(R3O)mR4
wherein R1: any one of alkyl group, alkoxy group and aryl group;
R2: alkylene group having a carbon number of 2-4;
R3: alkylene group having a carbon number of 2-4;
R4: hydrogen or alkyl group.
In this essential feature, there is used, as a working fluid for a compressor of a refrigerating/air-conditioning machine, a lubricating oil with an added compound together with a HFC refrigerant, said compound has the miscibility with the HFC refrigerant and the solubility with contaminants generated in the use of the HFC refrigerant. Therefore, the deflection is not caused in the ratio between the above lubricating oil and the HFC refrigerant, and, consequently, the reduction in the efficiency for washing capillary tubes and expansion valves can be prevented. That is, according to the present invention, a high-reliable refrigerating/air-conditioning machine using a HFC refrigerant can be obtained at a low price without any modification thereof.
Further, one embodiment is characterized in that the amount of the above compound to be added to the lubricating oil is not less than 0.1 wt % and not more than 20 wt %.
In this essential feature, since the amount of the above compound to be added is 0.1 wt % or more, the flow reduction rate for refrigerating/air-conditioning machines can be decreased below the rate in the case where the previous HFC refrigerant/polyvinyl ether (or polyol ester) lubricating oils are used. Further, since the addition amount of the above compound having a low volume insulation resistivity is 20 wt % or less, it is not possible that the volume insulation resistivity for the whole lubricating oil becomes too small and, consequently, an increase in the leakage current from a hermetic motor makes the motor unusable.
Further, one embodiment is characterized in that the amount of the above compound to be added to the lubricating oil is not less than 2 wt % and not more than 10 wt %.
In this essential feature, the flow reduction rate in the refrigerating/air-conditioning machine can be decreased to 0%-17%. Therefore, choking caused by contaminants in capillary tubes and expansion valves can be effectively prevented.
Further, one embodiment is characterized in that the viscosity of the above compound at 40xc2x0 C. is 70 cSt or less.
In this essential feature, since the viscosity of the above compound at 40xc2x0 C. is 70 cSt or less, the molecular weight of the above compound should be below several thousands. Therefore, clogging with the above compound itself, caused by an increase in the viscosity to several ten thousands in a low-temperature region, such as capillary tubes, can be prevented.
Further, one embodiment is characterized in that the carbon number of either of the alkylene groups R2 and R3 in the above compound is 4.
In this essential feature, since the carbon number of the alkylene group is large, the solubility with HFC refrigerants or contaminants is enhanced, and, consequently, the flow reduction rate can be sufficiently decreased to 0%-10%. Therefore, choking caused by contaminants in capillary tubes and expansion valves can be prevented more effectively.
In addition, the present invention features a refrigerating/air-conditioning machine equipped with a compressor using, as a working fluid, a HFC refrigerant and a polyvinyl ether lubricating oil, to which a compound having the following general formula is added at an amount of not less than 5 wt % and not more than 10 wt %:
R1(C4H8O)n(R5O)mR4
wherein R1: any one of alkyl group, alkoxy group and aryl group;
R4: hydrogen or alkyl group;
R5: alkylene group having a carbon number of 2-3;
n/m: 1/9-10/0.
In this essential feature, since the above compound contains butylene oxide (C4H8O) having a carbon number of 4, the solubility with HFC refrigerants and contaminants is very good. Moreover, since the compound is added to a polyvinyl ether lubricating oil at an amount of not less than 5 wt %, the flow reduction rate in a refrigerating/air-conditioning machine can be sufficiently decreased to 0%-10%. Therefore, choking caused by contaminants in capillary tubes and expansion valves can be effectively prevented. Further, since the amount of the above compound to be added to the lubricating oil is 10 wt % or less, the reduction in volume insulation resistance for the whole lubricating oil can be decreased. Therefore, it is not possible that leakage current from a hermetic motor increases. That is, according to the present invention, a high-reliable refrigerating/air-conditioning machine using a HFC refrigerant can be obtained without any modification thereof.
Further, one embodiment is characterized in that the ratio n/m for n and m in the above general formula is 7/3 or more.
In this essential feature, since the ratio of n to m in the above general formula is 7/3 or more, the proportion of the butylene oxide is large and, consequently, the flow reduction rate in a refrigerating/air-conditioning machine can be further decreased to 0%-5%. Therefore, choking caused by contaminants in capillary tubes and expansion valves can be prevented more effectively.
Further, one embodiment is characterized in that the viscosity of the above compound at 40xc2x0 C. is more than 32 cSt and not more than 70 cSt.
In this essential feature, since the viscosity of the above compound at 40xc2x0 C. is above 32 cSt, the reduction in volume insulation resistance for the whole lubricating oil can be decreased. Further, since the viscosity of the above compound is 70 cSt or less, the molecular weight of the above compound should be below several thousands and, consequently, clogging with the above compound itself, caused by an increase in the viscosity to several ten-thousands in a low-temperature region, such as capillary tubes, can be prevented.